Imaging lens

ABSTRACT

There is provided an imaging lens with high resolution which effectively achieves low-profileness while maintaining the wide field of view, and favorably corrects aberrations. 
     The imaging lens comprising a first lens having negative refractive power, a second lens having positive refractive power, a third lens, a fourth lens having positive refractive power, a fifth lens having negative refractive power as a double-sided aspheric lens, and a sixth lens as a double-sided aspheric lens, wherein the first lens has a concave surface facing the image side, and the aspheric surface on the image side of the sixth lens is formed as a concave surface near the optical axis and has at least one pole point at an off-axial point, and a below conditional expression (1) is satisfied:
 
ω≥45°  (1)
 
where
     ω: a half field of view.

The present application is based on and claims priority of Japanesepatent applications No. 2016-215076 filed on Nov. 2, 2016, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an imaging lens which forms an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in a compact imaging device, and more particularly to animaging lens which is built in an imaging device mounted in anincreasingly compact and low-profile smartphone and mobile phone, a PDA(Personal Digital Assistant), a game console, PC, and an informationterminal such as a robot, moreover, a home appliance and an automobilewith the camera function.

Description of the Related Art

In recent years, it becomes common that camera function is mounted inmany information terminals. Furthermore, products have been made oneafter another, such as home appliances with a camera, which consumer'sconvenience is excellent. Demand of products such as the home appliancesand the information terminals with the camera function is moreincreased, and development of products will be rapidly made accordingly.

In a conventional art, as an imaging lens mounted in such informationterminals, for example, following Patent Document 1 discloses an imaginglens comprising 6 lenses.

Patent Document 1 (JP-A-2016-031531) discloses an imaging lenscomprising, in order from an object side to an image side along with anoptical axis, a first lens element, a second lens element, a third lenselement, a fourth lens element, a fifth lens element and a sixth lenselement, each having an object-side surface facing an object side and animage-side surface facing an image side, and refractive power.

In the imaging lens disclosed in the above Patent Document 1, field ofview is wide about 140 to 160 degrees, however, a ratio of total tracklength to diagonal length is about 1.3 to 1.5 and low-profileness is notsufficiently satisfied. Additionally, when the low-profileness is madeusing lens composition disclosed in the above Patent Document 1, thereis a problem that aberration correction in peripheral area is verydifficult, and excellent optical performance is not be obtained.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems, andan object of the present invention is to provide an imaging lens withhigh resolution which effectively achieves low-profileness whilemaintaining a wide field of view, and favorably corrects aberrations.

Here, “wide field of view” implies that a half field of view in a rangecapable of photographing is 45 degrees or more (namely the field of viewis 90 degrees or more). “Low-profile” implies that total track length isless than 5.5 mm, and a ratio of total track length to diagonal lengthis less than 1.1. Regarding the ratio of total track length to diagonallength, the diagonal length of the effective imaging plane of the imagesensor is equal to the diameter of an effective image circle whoseradius is the vertical height from an optical axis to the point where alight ray incident on the imaging lens at a maximum field of view entersthe image plane, that is, the maximum image height.

Regarding terms used in the present invention, unless otherwise noted, aconvex surface or a concave surface of lens surfaces implies that theparaxial portion (portion near the optical axis) of the surface isconvex or concave. The pole point implies that a point on an asphericsurface at which a tangential plane intersects the optical axisperpendicularly. The total track length is, for example, defined as adistance along the optical axis from an object-side surface of anoptical element nearest to the object side to the imaging plane, whenthickness of the optical element such as an IR cut filter or a coverglass located between the last lens and the imaging plane of the imagesensor is regarded as an air. Furthermore, the effective diameterimplies the diameter of the circle whose radius is the vertical heightfrom the optical axis to the intersection point of the lens surface andthe light ray among pencil of light rays arriving at the maximum imageheight, which passes the farthest area from the optical axis.

In order to achieve the above object, an imaging lens according to thepresent invention comprises, in order from an object side to an imageside, a first lens having negative refractive power, a second lenshaving positive refractive power, a third lens, a fourth lens havingpositive refractive power, a fifth lens having negative refractive poweras a double-sided aspheric lens, and a sixth lens as a double-sidedaspheric lens. The first lens has a concave surface facing the imageside, and the aspheric surface on the image side of the sixth lens isformed as a concave surface near the optical axis and has at least onepole point at an off-axial point, and a below conditional expression (1)is satisfied:ω≥45°  (1)whereω: a half field of view.

According to the above structure, the first lens has negative refractivepower and the concave surface facing the image side, and light rayincident to the first lens over wide field of view enters the secondlens in nearly parallel along the optical axis.

The second lens has positive refractive power and contributes tolow-profileness.

The fourth lens keeps proper balance of the positive refractive powersof the second lens and the fourth lens, achieves low-profileness, andcorrects astigmatism and field curvature.

The fifth lens has negative refractive power and corrects chromaticaberration. The fifth lens is a double-sided aspheric lens, and controlslight ray incident angle to the image sensor and favorably correctsdistortion.

The sixth lens has the concave surface facing the image side near theoptical axis and ensures a back focus. The sixth lens is a double-sidedaspheric lens, and an aspheric surface on the image side has the polepoint and changes to the convex surface at an area apart from theoptical axis. Thus having such aspheric surfaces, together with thefifth lens, the sixth lens also controls the light ray incident angle tothe image sensor and favorably corrects distortion.

According to the imaging lens having the above structure, it ispreferable that a below conditional expression (a) is satisfied toobtain the imaging lens which is made sufficiently low-profile:TTL/2ih≤1.1  (a)whereTTL: the total track length,ih: a maximum image height.

According to the imaging lens having the above structure, it ispreferable that the first lens satisfies a below conditional expression(2):0.1<SAG L1R/r2<0.6  (2)whereSAG L1R: an amount of sag at the peripheral area of the effectivediameter of the image-side surface of the first lens,r2: a curvature radius of the image-side surface of the first lens.

Conditional expression (2) defines a condition for improvingfacilitation of the wide field of view and manufacturing. When theconditional expression (2) is satisfied, while maintaining a properangle of the right lay emitted from the first lens, the right lay entersthe second lens. Accordingly, the wide field of view can be easilyachieved. Furthermore, uneven thickness of the first lens is suppressedand manufacturing is facilitated.

According to the imaging lens having the above structure, it ispreferable that the first lens satisfies a below conditional expression(3):0.5<r2/f<1.5  (3)wherer2: the curvature radius of the image-side surface of the first lens,f: a focal length of the overall optical system.

The conditional expression (3) defines a condition for improving thefacilitation of the wide field of view, and for favorably correcting theaberrations. When the conditional expression (3) is satisfied, thecurvature radius of the image-side surface of the first lens becomesappropriate, and while maintaining a proper angle of the right layemitted from the first lens, the right lay enters the second lens.Accordingly, the wide field of view can be easily achieved.

According to the imaging lens having the above structure, it ispreferable that the second lens has the convex surface facing the objectside near the optical axis. Thus configured, the total track length isshortened.

According to the imaging lens having the above structure, it ispreferable that the third lens has the negative refractive power and theconcave surface facing the image side near the optical axis. Thusconfigured, chromatic aberration occurred at the first lens and thesecond lens is favorably corrected.

According to the imaging lens having the above structure, it ispreferable that the fourth lens has the convex surface facing the imageside near the optical axis. Thus configured, an off-axis light ray isguided to the fifth lens at a small refractive angle and the astigmatismand the field curvature is favorably corrected.

According to the imaging lens having the above structure, it ispreferable that the sixth lens is a meniscus lens having the negativerefractive power and the convex surface facing the object side near theoptical axis. Thus configured, together with the aspheric surface of theobject-side surface, the light ray incident angle to the image sensor iscontrolled. Furthermore, the sixth lens is the meniscus lens, therefore,uneven thickness of the sixth lens is suppressed and the manufacturingis facilitated.

According to the imaging lens having the above structure, it ispreferable that a below conditional expression (4) is satisfied:f2−f4>0  (4)wheref2: a focal length of the second lens,f4: a focal length of the fourth lens.

The conditional expression (4) defines a condition for effectivelyachieving proper corrections of astigmatism and field curvature based onrelationship of focal length of the second lens and focal length of thefourth lens. When the conditional expression (4) is satisfied, theastigmatism and the field curvature are favorably corrected.

According to the imaging lens having the above structure, it ispreferable that below conditional expressions (5), (6), (7), (8), (9)and (10) are satisfied:−2.5<f1/f<−1.0  (5)0.5<f2/f<1.5  (6)−6.0<f3/f<−1.5  (7)0.5<f4/f<1.5  (8)−6.0<f5/f<−1.5  (9)−2.5<f6/f<−1.0  (10)wheref1: a focal length of the first lens,f2: a focal length of the second lens,f3: a focal length of the third lens,f4: a focal length of the fourth lens,f5: a focal length of the fifth lens,f6: a focal length of the sixth lens,f: a focal length of the overall optical system.

The conditional expression (5) defines a condition for effectivelyachieving the facilitation of the wide field of view, and propercorrections of the field curvature and the distortion, based on a ratioof the focal length of the first lens and the focal length of theoverall optical system. When the conditional expression (5) issatisfied, the negative refractive power of the first lens is suppressedfrom being small, and while maintaining a proper angle of the right layemitted from the first lens, the right lay enters the second lens.Accordingly, the wide field of view can be easily achieved. Furthermore,the refractive power of the first lens against the focal length of theoverall optical system is suppressed from being too large, and the fieldcurvature and the distortion is favorably corrected.

The conditional expression (6) defines a condition for effectivelyachieving suppression of tolerance sensitivity and the aberrations, andshortening of the total track length, based on a ratio of the focallength of the second lens and the focal length of the overall opticalsystem. When the conditional expression (6) is satisfied, the positiverefractive power of the second lens is suppressed from being large, andthe tolerance sensitivity, spherical aberration and coma aberrationoccurred at the second lens is suppressed. When the positive refractivepower of the second lens is suppressed from being small, compositeprincipal points from the second lens to the fourth lens are movedtoward the object side, and the total track length is shortened.

The conditional expression (7) defines a condition for effectivelyachieving favorable correction of chromatic aberration and suppressionof tolerance sensitivity and the aberrations, based on a ratio of thefocal length of the third lens and the focal length of the overalloptical system. When the conditional expression (7) is satisfied, thenegative refractive power of the third lens is suppressed from beingsmall and chromatic aberration is favorably corrected. Additionally, thenegative refractive power of the third lens is suppressed from beinglarge and the tolerance sensitivity and the aberrations are suppressed.

The conditional expression (8) defines a condition for effectivelyachieving suppression of tolerance sensitivity and shortening of thetotal track length, based on a ratio of the focal length of the fourthlens and the focal length of the overall optical system. When theconditional expression (8) is satisfied, the positive refractive powerof the fourth lens is suppressed from being large and the tolerancesensitivity is suppressed. Additionally, the positive refractive powerof the fourth lens is suppressed from being small and the total tracklength is shortened.

The conditional expression (9) defines a condition for effectivelyachieving favorable correction of chromatic aberration and shortening ofthe total track length, based on a ratio of the focal length of thefifth lens and the focal length of the overall optical system. When theconditional expression (9) is satisfied, the negative refractive powerof the fifth lens is suppressed from being small and chromaticaberration is favorably corrected. Additionally, the negative refractivepower of the fifth lens is suppressed from being large and the totaltrack length is shortened.

The conditional expression (10) defines a condition for effectivelyachieving ensuring the back focus and shortening of the total tracklength, based on a ratio of the focal length of the sixth lens and thefocal length of the overall optical system. When the conditionalexpression (10) is satisfied, the negative refractive power of the sixthlens is suppressed from being small and the back focus is ensured.Additionally, the negative refractive power of the sixth lens issuppressed from being large and the total track length is shortened.

According to the imaging lens having the above structure, it ispreferable that a below conditional expression (11) is satisfied:1.0<f456/f<2.5  (11)wheref456: a composite focal length of the fourth lens, the fifth lens andthe sixth lens,f: a focal length of the overall optical system.

The conditional expression (11) defines a condition for effectivelyachieving favorable correction of the field curvature and shortening ofthe total track length, based on a ratio of the composite focal lengthof the fourth lens, the fifth lens and the sixth lens and the focallength of the overall optical system. When the conditional expression(11) is satisfied, the field curvature is favorably corrected and thetotal track length is shortened.

According to the imaging lens having the above structure, it ispreferable that a below conditional expression (12) is satisfied:0.2<t1/f<0.6  (12)wheret1: a distance along the optical axis between the first lens and thesecond lens,f: a focal length of the overall optical system.

The conditional expression (12) defines a condition for effectivelyachieving favorable correction of the aberrations and low-profileness,based on a ratio of distance along the optical axis between the firstlens and the second lens and the focal length of the overall opticalsystem. When the conditional expression (12) is satisfied, designfreedom of aspheric surface of the first lens is ensured, and theaberrations are favorably corrected and the total track length isshortened.

According to the imaging lens having the above structure, it ispreferable that a below conditional expression (13) is satisfied toobtain the imaging lens achieving the wide field of view and favorablycorrecting aberrations:0.5<CA1/ih<2.0  (13)whereCA1: an effective diameter of an object-side surface of the first lens,Ih: a maximum image height.

The conditional expression (13) defines a condition for effectivelyachieving the wide field of view and control of the light ray incidentangle to the image sensor, based on a ratio of the maximum image heightand the effective diameter of the object-side surface of the first lens.When the conditional expression (13) is satisfied, the proper effectivediameter of an object-side surface of the first lens against the imagesensor is obtained. Therefore, the wide field of view and control of thelight ray incident angle to the image sensor can be easily achieved.

According to the imaging lens having the above structure, it ispreferable that below conditional expressions (14) and (15) issatisfied:0.05<SAG L1F/CA1<0.50  (14)0.05<SAG L1R/CA2<0.50  (15)whereSAG L1F: an amount of sag at the peripheral area of the effectivediameter of the object-side surface of the first lens,SAG L1R: an amount of sag at the peripheral area of the effectivediameter of the image-side surface of the first lens,CA1: an effective diameter of the object-side surface of the first lens,CA2: an effective diameter of the image-side surface of the first lens.

The conditional expression (14) defines a condition for more improvingfacilitation of the wide field of view and manufacturing. When theconditional expression (14) is satisfied, the proper object-side surfaceof the first lens is obtained, and achieving the wide field of view andmanufacturing are more easily made.

The conditional expression (15) defines a condition for more improvingfacilitation of the wide field of view and manufacturing. When theconditional expression (15) is satisfied, while maintaining the properangle of the right lay emitted from the first lens, the right lay entersthe second lens. Accordingly, the wide field of view can be easilyachieved. Furthermore, uneven thickness of the first lens is suppressedand manufacturing is facilitated.

Effect of Invention

According to the present invention, there is provided a compact imaginglens with high resolution which effectively achieves low-profilenesswhile maintaining the wide field of view, and favorably correctsaberrations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a general configuration of an imaginglens in Example 1 according to the present invention;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1 according to the present invention;

FIG. 3 is a schematic view showing the general configuration of animaging lens in Example 2 according to the present invention;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2 according to the present invention;

FIG. 5 is a schematic view showing the general configuration of animaging lens in Example 3 according to the present invention;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3 according to the present invention;

FIG. 7 is a schematic view showing the general configuration of animaging lens in Example 4 according to the present invention;

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4 according to the present invention;

FIG. 9 is a schematic view showing the general configuration of animaging lens in Example 5 according to the present invention; and

FIG. 10 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 5 according to the present invention.

FIG. 11 is a schematic view showing the general configuration of animaging lens in Example 6 according to the present invention;

FIG. 12 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 6 according to the present invention;

FIG. 13 illustrates an effective diameter according to the presentinvention; and

FIG. 14 illustrates an amount of sag at the peripheral area of theeffective diameter of the first lens according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail referring to the accompanying drawings.

FIGS. 1, 3, 5, 7, 9 and 11 are schematic views showing the generalconfigurations of the imaging lenses in Examples 1 to 6 according to theembodiments of the present invention, respectively. Since all theseexamples have the same basic lens configuration, the generalconfiguration of an imaging lens according to this embodiment isexplained below mainly referring to the schematic view of Example 1.

As shown in FIG. 1, the imaging lens according to this embodiment formsan image of an object on an image sensor, and comprises in order from anobject side to an image side, a first lens L1 having negative refractivepower and a concave surface facing an image side near an optical axis X,a second lens L2 having positive refractive power, a third lens L3, afourth lens L4 having positive refractive power, a fifth lens L5 havingnegative refractive power as a double-sided aspheric lens, and a sixthlens L6 as a double-sided aspheric lens which has a concave surface nearthe optical axis X and at least one pole point at an off-axial point(namely, away from the optical axis) on the image-side surface.

A filter IR such as an IR cut filter and a cover glass is locatedbetween the sixth lens L6 and an image plane IM. The filter IR isomissible.

The first lens L1 is a meniscus lens which has the image-side surfacebeing concave near the optical axis X. Thus configured, a light ray iscapable of entering from wide angles, and while a proper angle of theright lay emitted from the first lens L1, the right lay enters thesecond lens L2. The first lens L1 is required to have the image-sidesurface being concave near the optical axis X. Additionally, as shown inExample 3 in FIG. 5, the first lens L1 may have a biconcave shape havingboth the object-side and the image-side surfaces being concave near theoptical axis X, or as shown in Example 5 in FIG. 9, may have theobject-side surface being plane and the image-side surface being concavenear the optical axis X.

The second lens L2 has a biconvex shape having both the object-side andimage-side surfaces being convex near the optical axis X. The secondlens L2 contributes to achieve low-profileness.

The third lens L3 has negative refractive power and a biconcave shapehaving both the object-side and the image-side surfaces being concavenear the optical axis X. The third lens L3 corrects spherical aberrationand chromatic aberration occurred at the first lens and the second lens.The third lens L3 is required to have the image-side surface beingconcave near the optical axis X, and as shown in Example 5 in FIG. 9,the third lens L3 may be a meniscus lens having the convex surfacefacing the object side near the optical axis X. Furthermore, the thirdlens L3 may have the object-side surface being plane.

The fourth lens L4 is a meniscus lens having the object-side surfacebeing concave and the image-side surface being convex near the opticalaxis X. By properly striking a balance between the refractive power ofthe fourth lens L4 and the refractive power of the second lens L2, thelow-profileness is achieved, and astigmatism and field curvature arecorrected. The fourth lens L4 is required to have the image-side surfacebeing convex near the optical axis X, and as shown in Example 5 in FIG.9, may have a biconvex shape having both the object-side and theimage-side surfaces being convex near the optical axis X.

The fifth lens L5 is a meniscus lens having the object-side surfacebeing concave and the image-side surface being convex near the opticalaxis X. The fifth lens L5 has negative refractive power and corrects thechromatic aberration. The fifth lens L5 is a double-sided aspheric lens,and controls the light ray incident angle to the image sensor andfavorably corrects distortion. As shown in Example 2 in FIG. 3, thefifth lens L5 may be a biconcave lens having both the object-side andthe image-side surfaces being concave near the optical axis X.Additionally, the fifth lens L5 may have either one of the object-sidesurface and the image-side surface being plane near the optical axis.

The sixth lens L6 has negative refractive power. Furthermore, the sixthlens L6 is a meniscus lens having the object-side surface being convexnear the optical axis X. The sixth lens L6 is a double-sided asphericlens, and the aspheric surface on the image side has a pole point andchanges to the convex surface at an area apart from the optical axis.Thus having such aspheric surfaces, together with the fifth lens, thesixth lens L6 also controls the light ray incident angle to the imagesensor and favorably corrects distortion.

The imaging lens according to the present embodiments satisfies a belowconditional expression (a) and the imaging lens being sufficiently madelow-profile is obtained:TTL/2ih1.1  (a)whereTTL: the total track length,ih: a maximum image height.

The imaging lens according to the present embodiments satisfies a belowconditional expression (1), and the imaging lens sufficiently achievingthe wide field of view is obtained:ω≥45°  (1)whereω: a half field of view.

The imaging lens according to the present embodiments satisfies a belowconditional expression (2), and the wide field of view is achieved andmanufacturing is facilitated:0.1<SAG L1R/r2<0.6  (2)whereSAG L1R: an amount of sag at the peripheral area of the effectivediameter of the image-side surface of the first lens,r2: the curvature radius of the image-side surface of the first lens.

Regarding the conditional expression (2), a below conditional expression(2a) is more preferable, and a conditional expression (2b) isparticularly preferable:0.1<SAG L1R/r2<0.55  (2a)0.15<SAG L1R/r2<0.5.  (2b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (3), and the wide field of view is achieved andaberrations are favorably corrected:0.5<r2/f<1.5  (3)wherer2: the curvature radius of the image-side surface of the first lens,f: the focal length of the overall optical system.

Regarding the conditional expression (3), a below conditional expression(3a) is more preferable, and a conditional expression (3b) isparticularly preferable:0.6<r2/f<1.3  (3a)0.65<r2/f<1.15.  (3b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (4), and relationship of a focal length of thesecond lens L2 and a focal length of the fourth lens L4 is properlydefined to effectively achieve proper correction of the astigmatism andthe field curvature:f2−f4>0  (4)wheref2: the focal length of the second lens,f4: the focal length of the fourth lens.

The imaging lens according to the present embodiments satisfies a belowconditional expression (5), and a ratio of the focal length of the firstlens L1 and the focal length of the overall optical system is properlydefined to effectively achieve facilitation of the wide field of viewand favorable correction of the field curvature and the distortion:−2.5<f1/f<−1.0  (5)wheref1: the focal length of the first lens,f: the focal length of the overall optical system.

Regarding the conditional expression (5), a below conditional expression(5a) is more preferable, and a conditional expression (5b) isparticularly preferable:−2.3<f1/f<−1.3  (5a)−2.2<f1/f<−1.5.  (5b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (6), and a ratio of the focal length of thesecond lens L2 and the focal length of the overall optical system isproperly defined to effectively achieve suppression of tolerancesensitivity and the aberrations and shortening of the total tracklength:0.5<f2/f<1.5  (6)wheref2: the focal length of the second lens,f: the focal length of the overall optical system.

Regarding the conditional expression (6), a below conditional expression(6a) is more preferable, and a conditional expression (6b) isparticularly preferable:0.7<f2/f<1.3  (6a)0.8<f2/f<1.2.  (6b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (7), and a ratio of the focal length of the thirdlens L3 and the focal length of the overall optical system is properlydefined to effectively achieve favorable correction of the chromaticaberration and suppression of the tolerance sensitivity and theaberrations:−6.0<f3/f<−1.5  (7)wheref3: the focal length of the third lens,f: the focal length of the overall optical system.

Regarding the conditional expression (7), a below conditional expression(7a) is more preferable, and a conditional expression (7b) isparticularly preferable:−5.5<f3/f<−1.8  (7a)−5.3<f3/f<−2.0.  (7b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (8), and a ratio of the focal length of thefourth lens L4 and the focal length of the overall optical system isproperly defined to effectively achieve suppression of the tolerancesensitivity and shortening of the total track length:0.5<f4/f<1.5  (8)wheref4: the focal length of the fourth lens,f: the focal length of the overall optical system.

Regarding the conditional expression (8), a below conditional expression(8a) is more preferable, and a conditional expression (8b) isparticularly preferable:0.5<f4/f<1.2  (8a)0.6<f4/f<1.0.  (8b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (9), and a ratio of the focal length of the fifthlens L5 and the focal length of the overall optical system is properlydefined to effectively achieve favorable correction of the chromaticaberration and shortening of the total track length:−6.0<f5/f<−1.5  (9)wheref5: the focal length of the fifth lens,f: the focal length of the overall optical system.

Regarding the conditional expression (9), a below conditional expression(9a) is more preferable, and a conditional expression (9b) isparticularly preferable:−5.0<f5/f<−1.7  (9a)−4.5<f5/f<−1.8.  (9b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (10), and a ratio of the focal length of thesixth lens L6 and the focal length of the overall optical system isproperly defined to effectively achieve ensuring a back focus andshortening of the total track length:−2.5<f6/f<−1.0  (10)wheref6: the focal length of the sixth lens,f: the focal length of the overall optical system.

Regarding the conditional expression (10), a below conditionalexpression (10a) is more preferable, and a conditional expression (10b)is particularly preferable:−2.3<f6/f<−1.2  (10a)−2.1<f6/f<−1.2.  (10b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (11), and a ratio of the composite focal lengthof the fourth lens, the fifth lens and the sixth lens and the focallength of the overall optical system is properly defined to effectivelyachieve favorable correction of the field curvature and shortening ofthe total track length:1.0<f456/f<2.5  (11)wheref456: the composite focal length of the fourth lens, the fifth lens andthe sixth lens,f: the focal length of the overall optical system.

Regarding the conditional expression (11), a below conditionalexpression (11a) is more preferable, and a conditional expression (11b)is particularly preferable:1.2<f456/f<2.3  (11a)1.3<f456/f<2.0.  (11b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (12), which is defined to effectively achievefavorable correction of the aberrations and shortening of total tracklength:0.2<t1/f<0.6  (12)wheret1: the distance along the optical axis between the first lens and thesecond lens,f: the focal length of the overall optical system.

Regarding the conditional expression (12), a below conditionalexpression (12a) is more preferable, and a conditional expression (12b)is particularly preferable:0.25<t1/f<0.58  (12a)0.28<t1/f<0.55.  (12b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (13), which is defined to effectively achieve thewide field of view and control of the light ray incident angle to theimage sensor:0.5<CA1/ih<2.0  (13)whereCA1: the effective diameter of an object-side surface of the first lens,Ih: the maximum image height.

Regarding the conditional expression (13), a below conditionalexpression (13a) is more preferable, and a conditional expression (13b)is particularly preferable:0.6<CA1/ih<1.7  (13a)0.7<CA1/ih<1.5.  (13b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (14), which is defined to effectively achievefacilitation of the wide field of view and manufacturing:0.05<SAG L1F/CA1<0.50  (14)whereSAG L1F: an amount of sag at the peripheral area of the effectivediameter of the object-side surface of the first lens,CA1: the effective diameter of the object-side surface of the firstlens.

Regarding the conditional expression (14), a below conditionalexpression (14a) is more preferable, and a conditional expression (14b)is particularly preferable:0.06<SAG L1F/CA1<0.30  (14a)0.07<SAG L1F/CA1<0.20.  (14b)

The imaging lens according to the present embodiments satisfies a belowconditional expression (15), which is defined to effectively achievefacilitation of the wide field of view and manufacturing:0.05<SAG L1R/CA2<0.50  (15)whereSAG L1R: an amount of sag at the peripheral area of the effectivediameter of the image-side surface of the first lens,CA2: the effective diameter of the image-side surface of the first lens.

Regarding the conditional expression (15), a below conditionalexpression (15a) is more preferable, and a conditional expression (15b)is particularly preferable:0.10<SAG L1R/CA2<0.45  (15a)0.20<SAG L1R/CA2<0.40.  (15b)

The invention is not limited to the embodiments specifically disclosed,and substitutions, modifications, and variations may be made to thepresent invention without departing from the object of the invention.

Regarding the imaging lens according to the present embodiments, it ispreferable to satisfy all of conditional expressions. By satisfying theconditional expression individually, operational advantage correspondingto each conditional expression can be obtained.

In this embodiment, the aspheric shapes of the surfaces of the asphericlens are expressed by Equation 1, where Z denotes an axis in the opticalaxis direction, H denotes a height perpendicular to the optical axis, Rdenotes a curvature radius, k denotes a conic constant, and A4, A6, A8,A10, A12, A14, and A16 denote aspheric surface coefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {\left( {k + 1} \right)\frac{H^{2}}{R^{2}}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, examples of the imaging lens according to this embodiment will beexplained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, ih denotes a maximum image height, and TTL denotesthe total track length. Additionally, i denotes surface number countedfrom the object side, r denotes a curvature radius, d denotes thedistance of lenses along the optical axis (surface distance), Nd denotesa refractive index at d-ray (reference wavelength), and νd denotes anabbe number at d-ray. As for aspheric surfaces, an asterisk (*) is addedafter surface number i.

Example 1

The basic lens data is shown below in Table 1.

Example 1 Unit mm f = 1.74 Fno = 2.42 ω(°) = 59.9 ih = 2.49 TTL = 4.42Surface Data Surface Curvature Surface Refractive Abbe Number Number iRadius r Distance d Index Nd vd (Object) Infinity Infinity 1* 6.7720.288 1.5443 55.86 2* 1.205 0.436 3(Stop) Infinity 0.092 4* 1.634 0.5151.5443 55.86 5* −1.547 0.149 6* −9.053 0.210 1.6510 21.52 7* 3.195 0.1058* −4.335 0.782 1.5348 55.66 9* −0.632 0.035 10*  −1.991 0.310 1.639123.25 11*  −3.546 0.050 12*  1.778 0.440 1.5348 55.66 13*  0.742 0.50014  Infinity 0.110 1.5168 64.20 15  Infinity 0.431 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 1 f1 = −2.74f456 = 2.43 2 4 f2 = 1.55 CA1 = 1.95 3 6 f3 = −3.60 CA2 = 1.17 4 8 f4 =1.29 SAG L1F = 0.27 5 10 f5 = −7.70 SAG L1R = 0.28 6 12 f6 = −2.80Aspheric Surface Data First Surface Second Surface Fourth Surface FifthSurface Sixth Surface Seventh Surface k 0.00000E+00 2.83986E+002.47910E+00 0.00000E+00 0.00000E+00 7.61528E−01 A4 4.40403E−015.83114E−01 2.74129E−02 −6.26256E+01  −1.60329E+00  −8.70183E−01  A6−4.84282E−01  6.00713E−01 −3.75983E−01  8.49792E−01 5.38048E−011.37465E+00 A8 4.15053E−01 −6.67438E+00  9.66005E−01 −1.12126E+00 4.19575E+00 −1.57055E+00  A10 −1.52367E−01  1.90574E+01 −1.92308E+00 4.11207E−01 −1.29396E+01  8.56445E−01 A12 −4.61470E−03  −1.21594E+01 0.00000E+00 0.00000E+00 1.33176E+01 −1.49455E−02  A14 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A160.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00Eighth Surface Ninth Surface Tenth Surface Eleventh Surface TwelfthSurface Thirteenth Surface k 0.00000E+00 −2.32485E+00  0.00000E+000.00000E+00 0.00000E+00 −4.09446E+00  A4 1.74741E−01 −2.68765E−01 1.36592E−01 1.83882E−01 −2.39767E−01  −2.00244E−01  A6 −8.87073E−02 1.79338E−01 7.22718E−01 3.28525E−01 −5.10307E−03  1.09283E−01 A82.58502E−01 1.00372E+00 −1.89771E+00  −9.50716E−01  2.89054E−03−4.51186E−02  A10 −1.87120E+00  −3.44653E+00  1.99535E+00 9.08022E−016.15432E−02 9.70167E−03 A12 2.88222E+00 5.02706E+00 −1.31341E+00 −4.35087E−01  −4.75942E−02  −1.97692E−04  A14 −1.47680E+00 −3.86363E+00  5.11826E−01 1.05641E−01 1.36563E−02 −2.96542E−04  A160.00000E+00 1.30044E+00 8.32630E−02 −1.04117E−02  −1.45718E−03 3.63276E−05

The imaging lens in Example 1 satisfies conditional expressions (a) and(1) to (15) as shown in Table 7.

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at wavelengths of F-ray (486 nm), d-ray(588 nm), and C-ray (656 nm). The astigmatism diagram shows the amountof aberration at d-ray on a sagittal image surface S and on tangentialimage surface T (same as FIG. 4, FIG. 6, FIG. 8, FIG. 10 and FIG. 12).As shown in FIG. 2, each aberration is corrected favorably.

Example 2

The basic lens data is shown below in Table 2.

Example 2 Unit mm f = 1.63 Fno = 2.39 ω(°) = 60.1 ih = 2.49 TTL = 4.90Surface Data Surface Curvature Surface Refractive Abbe Number Number iRadius r Distance d Index Nd vd (Object) Infinity Infinity 1* 11.8090.345 1.5348 55.66 2* 1.202 0.883 3(Stop) Infinity −0.009 4* 1.827 0.6971.5443 55.86 5* −1.405 0.198 6* 23.439 0.210 1.6503 21.54 7* 2.312 0.1208* −159.598 0.737 1.5348 55.66 9* −0.747 0.035 10*  −2.987 0.310 1.639123.25 11*  82.236 0.051 12*  1.977 0.410 1.5348 55.66 13*  0.862 0.25014  Infinity 0.210 1.5168 64.20 15  Infinity 0.520 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 1 f1 = −2.53f456 = 3.13 2 4 f2 = 1.58 CA1 = 2.69 3 6 f3 = −3.96 CA2 = 1.59 4 8 f4 =1.40 SAG L1F = 0.48 5 10 f5 = −4.50 SAG L1R = 0.56 6 12 f6 = −3.27Aspheric Surface Data First Surface Second Surface Fourth Surface FifthSurface Sixth Surface Seventh Surface k 0.00000E+00 5.31502E−01−3.36243E+00  0.00000E+00 0.00000E+00 4.00696E−01 A4 3.71110E−014.86718E−01 −4.24428E−02  −4.06448E−01  −8.91305E−01  −5.97792E−01  A6−3.49809E−01  1.00383E+00 −6.67505E−01  −3.11136E−01  −3.19409E−01 5.61063E−01 A8 2.54180E−01 −5.01632E+00  2.84787E+00 1.11316E+002.99668E+00 −1.48239E−01  A10 −1.06048E−01  1.08784E+01 −1.37578E+01 −3.20483E+00  −8.05660E+00  −4.60255E−01  A12 1.68999E−02 −8.02150E+00 0.00000E+00 0.00000E+00 7.22205E+00 3.77686E−01 A14 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A160.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00Eighth Surface Ninth Surface Tenth Surface Eleventh Surface TwelfthSurface Thirteenth Surface k 0.00000E+00 −3.02592E+00 0.00000E+000.00000E+00 0.00000E+00 −6.45245E+00 A4 −1.45604E−01  −1.67774E−013.05311E−01 4.19085E−01 −1.74202E−01  −1.28923E−01 A6 7.35653E−01−3.02623E−02 −3.17984E−01  −6.87332E−01  −2.99644E−03   4.27165E−02 A8−1.65845E+00   1.20562E+00 −8.51208E−02  5.47065E−01 1.37171E−03−1.64241E−02 A10 2.04582E+00 −2.98400E+00 2.99387E−01 −2.73205E−01 2.36033E−02  4.82842E−03 A12 −1.44250E+00   3.57018E+00 −2.60502E−01 8.64238E−02 −1.47522E−02  −3.35157E−04 A14 3.84760E−01 −2.16250E+001.03329E−01 −1.56533E−02  3.42094E−03 −1.24427E−04 A16 0.00000E+00 5.29046E−01 1.50137E−02 1.21529E−03 −2.95009E−04   1.68283E−05

The imaging lens in Example 2 satisfies conditional expressions (a) and(1) to (15) as shown in Table 7.

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 2. As shown in FIG. 4, eachaberration is corrected favorably.

Example 3

The basic lens data is shown below in Table 3.

Example 3 Unit mm f = 1.89 Fno = 2.25 ω(°) = 60.0 ih = 2.28 TTL = 4.57Surface Data Surface Curvature Surface Refractive Abbe Number Number iRadius r Distance d Index Nd vd (Object) Infinity Infinity 1* −1984.0210.538 1.5348 55.66 2* 1.962 0.629 3(Stop) Infinity −0.043 4* 1.754 0.5841.5443 55.86 5* −2.754 0.096 6* −177.042 0.210 1.6503 21.54 7* 6.4500.110 8* −11.527 0.645 1.5348 55.66 9* −0.666 0.035 10*  −2.640 0.3101.6391 23.25 11*  15.473 0.149 12*  1.966 0.398 1.5348 55.66 13*  0.7730.290 14  Infinity 0.145 1.5168 64.20 15  Infinity 0.525 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length 1 1 f1 =−3.67 f456 = 3.56 2 4 f2 = 2.06 CA1 = 3.00 3 6 f3 = −9.56 CA2 = 1.62 4 8f4 = 1.29 SAG L1F = 0.30 5 10 f5 = −3.51 SAG L1R = 0.34 6 12 f6 = −2.69Aspheric Surface Data First Surface Second Surface Fourth Surface FifthSurface Sixth Surface Seventh Surface k 0.00000E+00 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 1.43539E−013.90095E−01 4.33654E−03 −6.46283E−01  −8.26642E−01  −3.86847E−01  A6−8.83772E−02  −2.67894E−01  −6.41647E−01  9.17502E−01 4.96005E−018.88156E−01 A8 4.82799E−02 6.80042E−01 1.97997E+00 −2.45505E+00 1.25283E+00 −1.51335E+00  A10 −1.64677E−02  −3.79474E−01  −6.35760E+00 6.35850E−01 −7.75115E+00  9.44637E−01 A12 2.28611E−03 0.00000E+000.00000E+00 0.00000E+00 1.05420E+01 1.96700E−01 A14 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A160.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00Eighth Surface Ninth Surface Tenth Surface Eleventh Surface TwelfthSurface Thirteenth Surface k 0.00000E+00 −3.16023E+00 0.00000E+000.00000E+00  0.00000E+00 −4.65433E+00  A4 −2.55928E−01  −2.54785E−015.56199E−01 4.16255E−01 −1.72099E−01 −1 .25077E−01  A6 1.76492E+00 6.34072E−01 −6.12178E−01  −5.72207E−01  −5.63640E−03 6.58266E−02 A8−4.22142E+00  −1.33848E−01 1.08046E−01 3.38187E−01 −3.18739E−03−4.21030E−02  A10 5.51485E+00 −2.34264E+00 1.71282E−01 −8.46553E−02  4.51248E−02 1.62408E−02 A12 −4.10168E+00   5.71799E+00 −1.20888E−01 −6.23633E−03  −3.21187E−02 −2.88270E−03  A14 1.20191E+00 −5.45873E+002.84071E−02 8.00436E−03  8.84350E−03 8.15540E−05 A16 0.00000E+00 1.87436E+00 −4.72685E−03  −1.26107E−03  −8.93978E−04 2.32413E−05

The imaging lens in Example 3 satisfies conditional expressions (a) and(1) to (15) as shown in Table 7.

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 3. As shown in FIG. 6, eachaberration is corrected favorably.

Example 4

The basic lens data is shown below in Table 4.

Example 4 Unit mm f = 1.91 Fno= 2.24 ω(°) = 60.0 ih = 2.28 TTL = 4.60Surface Data Surface Curvature Surface Refractive Abbe Number Number iRadius r Distance d Index Nd vd (Object) Infinity Infinity 1* −1984.0210.453 1.5348 55.66 2* 2.131 0.751 3(Stop) Infinity −0.037 4* 1.666 0.5561.5443 55.86 5* −2.519 0.125 6* 39.261 0.230 1.6503 21.54 7* 3.404 0.1108* −20.071 0.639 1.5348 55.66 9* −0.668 0.035 10*  −2.403 0.365 1.639123.25 11*  90.173 0.129 12*  2.040 0.380 1.5348 55.66 13*  0.746 0.40014  Infinity 0.145 1.5168 64.20 15  Infinity 0.368 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 1 f1 = −3.98f456 = 3.58 2 4 f2 = 1.93 CA1 = 2.93 3 6 f3 = −5.75 CA2 = 1.74 4 8 f4 =1.28 SAC L1F = 0.28 5 10 f5 = −3.66 SAC L1R = 0.38 6 12 f6 = −2.45Aspheric Surface Data First Surface Second Surface Fourth Surface FifthSurface Sixth Surface Seventh Surface k 0.00000E+00 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 1.59931E−013.52166E−01 −7.06583E−03  −4.58990E−01  −7.30950E−01  −4.33279E−01  A6−9.56205E−02  −1.57245E−01  −5.21484E−01  8.26557E−01 4.21595E−019.06329E−01 A8 4.79054E−02 3.36255E−01 1.45943E+00 −2.57841E+00 1.53818E+00 −1.47861E+00  A10 −1.62933E−02  −1.96624E−01  −4.66842E+00 9.41937E−01 −8.44883E+00  8.22954E−01 A12 2.22134E−03 0.00000E+000.00000E+00 0.00000E+00 1.05420E+01 1.96700E−01 A14 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A160.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00Eighth Surface Ninth Surface Tenth Surface Eleventh Surface TwelfthSurface Thirteenth Surface k 0.00000E+00 −3.22727E+00 0.00000E+000.00000E+00 0.00000E+00 −4.81957E+00  A4 −2.00309E−01  −2.03488E−015.63669E−01 4.07086E−01 −2.05033E−01  −1.48101E−01  A6 1.71872E+00 6.56608E−01 −6.32707E−01  −5.74794E−01  1.15316E−02 7.83579E−02 A8−4.22372E+00  −2.03342E−01 7.91350E−02 3.38045E−01 −3.82623E−03 −4.37351E−02  A10 5.54648E+00 −2.31712E+00 1.80417E−01 −8.42641E−02 4.46792E−02 1.60705E−02 A12 −4.10168E+00   5.71799E+00 −1.20888E−01 −5.92152E−03  −3.22016E−02  −2.85642E−03  A14 1.20191E+00 −5.45873E+002.84071E−02 8.02353E−03 8.83820E−03 1.00351E−04 A16 0.00000E+00 1.87436E+00 −4.72685E−03  −1.30936E−03  −8.83335E−04  1.84999E−05

The imaging lens in Example 4 satisfies conditional expressions (a) and(1) to (15) as shown in Table 7.

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 4. As shown in FIG. 8, eachaberration is corrected favorably.

Example 5

The basic lens data is shown below in Table 5.

Example 5 Unit mm f = 2.03 Fno = 2.23 ω(°) = 60.0 ih = 2.28 TTL = 4.64Surface Data Surface Curvature Surface Refractive Abbe Number Number iRadius r Distance d Index Nd vd (Object) Infinity Infinity 1* Infinity0.355 1.5348 55.66 2* 2.245 0.846 3(Stop) Infinity −0.064 4* 1.543 0.5621.5443 55.86 5* −4.878 0.125 6* 5.402 0.230 1.5503 21.54 7* 2.674 0.1108* 43.709 0.629 1.5348 55.66 9* −0.770 0.035 10*  −3.328 0.365 1.639123.25 11*  8.919 0.281 12*  2.717 0.380 1.5348 55.66 13*  0.896 0.40014  Infinity 0.110 1.5168 64.20 15  Infinity 0.317 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 1 f1 = −4.20f456 = 3.95 2 4 f2 = 2.22 CA1 = 2.93 3 6 f3 = −8.42 CA2 = 1.88 4 8 f4 =1.42 SAG L1F = 0.26 5 10 f5 = −3.75 SAG L1R = 0.42 6 12 f6 = −2.70Aspheric Surface Data First Surface Second Surface Fourth Surface FifthSurface Sixth Surface Seventh Surface k 0.00000E+00 0.00000E+000.00000E−00 0.00000E+00 0.00000E+00 0.00000E+00 A4 1.72875E−013.20721E−01 5.88135E−03 −3.90211E−01  −6.47512E−01  −4.11872E−01  A6−1.08661E−01  −1.05164E−01  −3.11728E−01  3.43197E−01 −2.56901E−01 5.93659E−01 A8 4.63623E−02 1 .24568E−01 9.08916E−01 −1.28559E+00 2.49035E+00 −1.06887E+00  A10 −1.34416E−02  −6.53543E−02  −2.76101E+00 7.27879E−02 −9.45186E+00  5.54355E−01 A12 1.73868E−03 0.00000E+000.00000E+00 0.00000E+00 1.05420E+01 1.96700E−01 A14 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A160.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00Eighth Surface Ninth Surface Tenth Surface Eleventh Surface TwelfthSurface Thirteenth Surface k 0.00000E+00 −3.26363E+00 0.00000E+000.00000E+00 0.00000E+00 −4.82616E+00  A4 −2.70368E−01  −2.10357E−014.46342E−01 3.14351 E−01 −2.41376E−01  −1.70148E−01  A6 1.73821E+00 6.12589E−01 −5.73026E−01  −5.39626E−01  4.85809E−02 9.37351E−02 A8−4.33791E+00  −4.87581E−01 −4.61254E−02  3.43589E−01 −8.64242E−03 −5.01025E−02  A10 5.68448E+00 −1.99787E+00 2.58990E−01 −8.77252E−02 4.35727E−02 1.64341E−02 A12 −4.10168E+00   5.71799E+00 −1.20260E−01 −6.14956E−03  −3.15635E−02  −2.76239E−03  A14 1.20191E+00 −5.45873E+002.84071E−02 8.15030E−03 8.64100E−03 1.82605E−04 A16 0.00000E+00 1.87436E+00 −4.72685E−03  −1.33079E−03  −8.53991E−04  1.15576E−06

The imaging lens in Example 5 satisfies conditional expressions (a) and(1) to (15) as shown in Table 7.

FIG. 10 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 5. As shown in FIG. 10,each aberration is corrected favorably.

Example 6

The basic lens data is shown below in Table 6.

Example 6 Unit mm f = 2.04 Fno = 2.24 ω(°) = 59.8 ih = 2.28 TTL = 4.64Surface Data Surface Curvature Surface Refractive Abbe Number Number iRadius r Distance d Index Nd vd (Object) Infinity Infinity 1* Infinity0.355 1.5348 55.66 2* 2.265 0.838 3(Stop) Infinity −0.072 4* 1.514 0.5501.5443 55.86 5* −5.955 0.125 6* 6.172 0.220 1.6503 21.54 7* 2.867 0.1108* 36.388 0.641 1.5348 55.66 9* −0.789 0.035 10*  −3.810 0.365 1.639123.25 11*  7.308 0.300 12*  2.298 0.380 1.5348 55.66 13*  0.865 0.50014  Infinity 0.110 1.5168 64.20 15  Infinity 0.222 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 1 f1 = −4.23f456 = 3.71 2 4 f2 = 2.28 CA1 = 2.90 3 6 f3 = −8.46 CA2 = 1.86 4 8 f4 =1.45 SAC L1F = 0.26 5 10 f5 = −3.87 SAC L1R = 0.41 6 12 f6 = −2.86Aspheric Surface Data First Surface Second Surface Fourth Surface FifthSurface Sixth Surface Seventh Surface k 0.00000E+00 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 1.69505E−013.20721E−01 2.47869E−02 −3.56643E−01  −6.46652E−01  −4.24558E−01  A6−9.80824E−02  −1.07595E−01  −2.99024E−01  1.65878E−01 −4.28751E−01 5.58791E−01 A8 3.97059E−02 1.87662E−01 9.44770E−01 −9.33836E−01 2.44503E+00 −1.05792E+00  A10 −1.19501E−02  −1.17522E−01  −2.71258E+00 −2.63833E−01  −8.97831E+00  7.07424E−01 A12 1.62839E−03 0.00000E+000.00000E+00 0.00000E+00 1.05420E+01 1.96700E−01 A14 0.00000E+000.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A160.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00Eighth Surface Ninth Surface Tenth Surface Eleventh Surface TwelfthSurface Thirteenth Surface k 0.00000E+00 −3.56367E+00 0.00000E+000.00000E+00 0.00000E+00 −4.51473E+00 A4 −2.76251E−01  −2.76503E−014.27935E−01 3.04032E−01 −2.77926E−01  −1.69988E−01 A6 1.70020E+00 7.14179E−01 −5.59142E−01  −5.39856E−01  6.51094E−02  8.97879E−02 A8−4.30599E+00  −6.05258E−01 −5.10738E−02  3.46777E−01 −1.17695E−02 −4.67236E−02 A10 5.68225E+00 −1.95804E+00 2.80629E−01 −8.74799E−02 4.26886E−02  1.61170E−02 A12 −4.10168E+00   5.71799E+00 −1.20260E−01 −6.69764E−03  −3.11569E−02  −2.89685E−03 A14 1.20191E+00 −5.45873E+002.84071E−02 7.97562E−03 8.59027E−03  1.84517E−04 A16 0.00000E+00 1.87436E+00 −4.72685E−03  −1.23734E−03  −8.51266E−04   5.30290E−06

The imaging lens in Example 6 satisfies conditional expressions (a) and(1) to (15) as shown in Table 7.

FIG. 12 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 6. As shown in FIG. 12,each aberration is corrected favorably.

As explained above, according to the imaging lens related to the presentembodiments, there can be provided the imaging lens with high resolutionwhich achieves low-profileness and favorably corrects aberrations,wherein the wide field of view having the field of view (2ω) is 90degrees or more is achieved, the total track length is less than 5.5 mm,and the ratio of total track length to diagonal length (TTL/2ih) is lessthan 1.1.

In table 7, values of conditional expressions (a), (1) to (15) relatedto the Examples 1 to 6 are shown.

TABLE 7 Conditional Conditional Conditional Conditional ConditionalConditional Conditional Conditional Expression Expression ExpressionExpression Expression Expression Expression Expression (a) (1) (2) (3)(4) (5) (6) (7) TTL/2IH ω SAG L1R/r2 r2/f f2 − f4 > 0 f1/f f2/f f3/fExample1 0.89 59.9 0.23 0.69 0.26 −1.57 0.89 −2.07 Example2 0.98 60.10.47 0.74 0.18 −1.55 0.97 −2.43 Example3 1.00 60.0 0.18 1.04 0.77 −1.941.09 −5.07 Example4 1.01 60.0 0.18 1.12 0.65 −2.09 1.01 −3.02 Example51.02 60.0 0.19 1.11 0.80 −2.07 1.10 −4.15 Example6 1.02 59.8 0.18 1.110.82 −2.08 1.12 −4.15 Conditional Conditional Conditional ConditionalConditional Conditional Conditional Conditional Expression ExpressionExpression Expression Expression Expression Expression Expression (14)(15) (8) (9) (10) (11) (12) (13) SAG L1F/ SAG L1R/ f4/f f5/f f6/f f456/ft1/f CA1/ih CA1 CA2 Example1 0.74 −4.42 −1.61 1.39 0.30 0.78 0.14 0.24Example2 0.86 −2.76 −2.01 1.92 0.54 1.08 0.18 0.35 Example3 0.69 −1.86−1.43 1.89 0.31 1.31 0.10 0.21 Example4 0.67 −1.92 −1.29 1.88 0.37 1.280.10 0.22 Example5 0.70 −1.85 −1.33 1.95 0.39 1.28 0.09 0.22 Example60.71 −1.90 −1.40 1.82 0.38 1.27 0.09 0.22

When the imaging lens having six lenses according to the presentinvention is applied to the imaging device mounted in an increasinglycompact and low-profile smartphone and a portable terminal device, agame console, PC, and an information terminal such as a robot, moreover,a home appliance and an automobile with the camera function,contribution is made to the low-profileness and the wide field of viewfor the camera, and high-performance can be achieved.

What is claimed is:
 1. An imaging lens forming an image of an object ona solid-state image sensor, comprising in order from an object side toan image side, a first lens having negative refractive power, a secondlens, a third lens, a fourth lens, a fifth lens having negativerefractive power and is a double-sided aspheric lens, and a sixth lenshaving negative refractive power and is a double-sided aspheric lens,wherein the third lens has a meniscus shape near an optical axis, andthe sixth lens has at least one pole point at an off-axial point on theimage-side surface, and below conditional expressions (10b) and (12) aresatisfied:−2.1<f6/f<−1.2.  (10b)0.2<t1/f<0.6  (12) where f6: a focal length of the sixth lens, f: afocal length of the overall optical system, and t1: a distance along theoptical axis between the first lens and the second lens.
 2. The imaginglens according to claim 1, wherein the first lens has a concave surfacefacing the image side near the optical axis.
 3. The imaging lensaccording to claim 1, wherein the second lens having positive refractivepower, the third lens having negative refractive power, and the fourthlens having positive refractive power.
 4. The imaging lens according toclaim 1, wherein a conditional expression below is satisfied:ω≥45°  (1) where ω: a half field of view.
 5. The imaging lens accordingto claim 1, wherein a conditional expression below is satisfied:0.1<SAG L1R/r2<0.6  (2) where SAG L1R: an amount of sag at theperipheral area of the effective diameter of the image-side surface ofthe first lens, r2: a curvature radius of the image-side surface of thefirst lens.
 6. The imaging lens according to claim 1, wherein aconditional expression below is satisfied:0.5<r2/f<1.5  (3) where r2: a curvature radius of an image-side surfaceof the first lens.
 7. The imaging lens according to claim 1, wherein thesecond lens has a convex surface facing the object side near the opticalaxis.
 8. The imaging lens according to claim 1, wherein the third lenshas a concave surface facing the image side near the optical axis. 9.The imaging lens according to claim 1, wherein the fourth lens has aconvex surface facing the image side near the optical axis.
 10. Theimaging lens according to claim 1, wherein the sixth lens has a convexsurface facing the object side near the optical axis and a concavesurface facing the image side near the optical axis.
 11. The imaginglens according to claim 1, wherein a conditional expression below issatisfied:f2−f4>0  (4) where f2: a focal length of the second lens, and f4: afocal length of the fourth lens.
 12. The imaging lens according to claim1, wherein conditional expressions below are satisfied:−2.5<f1/f<−1.0  (5)0.5<f2/f<1.5  (6)−6.0<f3/f<−1.5  (7)0.5<f4/f<1.5  (8)−6.0<f5/f<−1.5  (9) where f1: a focal length of the first lens, f2: afocal length of the second lens, f3: a focal length of the third lens,f4: a focal length of the fourth lens, and f5: a focal length of thefifth lens.
 13. The imaging lens according to claim 1, wherein aconditional expression below is satisfied:1.0<f456/f<2.5  (11) where f456: a composite focal length of the fourthlens, the fifth lens and the sixth lens.
 14. The imaging lens accordingto claim 1, wherein a conditional expression below is satisfied:0.5<CA1/ih<2.0  (13) where CA1: an effective diameter of an object-sidesurface of the first lens, and ih: a maximum image height.
 15. Theimaging lens according to claim 1, wherein conditional expressions beloware satisfied:0.05<SAG L1F/CA1<0.50  (14)0.05<SAG L1R/CA2<0.50  (15) where SAG L1F: an amount of sag at theperipheral area of the effective diameter of the object-side surface ofthe first lens, SAG L1R: an amount of sag at the peripheral area of theeffective diameter of the image-side surface of the first lens, CA1: aneffective diameter of the object-side surface of the first lens, andCA2: an effective diameter of the image-side surface of the first lens.